Four American presidents were driven to send weapons and soldier to fight in Vietnam due to the B. fear of communism spreading to many Asian countries. Around this time, US policymakers relied upon a concept of the "Domino Theory," which argued that if one nation were to fall to communism, countries nearby would then become communist.
Paper, allowed documents to be written and stored easier
Wheel, allowed faster transportation and could be used for pottery
Calendar, allowed for organized farming
